Ride hailing company Uber is warning passengers they may have to prove they are wearing a mask in vehicles before being taken on their journey.

In an email to customers the company writes “We said No Mask No Ride, We meant it. [We have] built the tech to back it up. Introducing Mask Verification – a new way to help protect riders and drivers.”

The concept is that any passenger who has been flagged for not wearing a mask will now have to take a selfie in the Uber app to verify that they are wearing one before their next ride. The company adds that anyone consistenly violating their mask policy will be removed from the Uber app.

The Company does not mention anywhere in its email whether those exempt from wearing a mask for physical or mental health issues will be allowed to travel. Users must click on an embedded link to find out.

Last month a survey of bus users suggested 63% of people with a medical exemption say they do not feel comfortable travelling without a face covering, with two out of five wearing one despite having a medical exemption, apparently because they feel pressured to do so.